1. Field of Invention
The present invention relates to an integrated circuit chip.
2. Description of Related Art
Laterally double-diffused metal oxide semiconductor (LDMOS) is a power source device commonly used in semiconductor processes. A LDMOS can provide a higher breakdown voltage (Vbd) and has a lower on-resistance (Ron) during operation. Hence, LDMOS is normally used as a high voltage device in power management IC. The CMOS-DMOS-Bipolar device (CDMOS) process and the HV LDMOS analog process are the process platform for power management IC.
As electron products become more digitized and miniaturized, the demands for voltage accuracy, stability and battery durability increase. In a typical semiconductor factory, a single LDMOS process can provide a high voltage device with a single voltage rating. In other words, each type of voltage rating high voltage device requires one corresponding IC. Hence, even a high voltage device in power management IC requires to have different voltage ratings, for example, 40 volts, 30 volts and 18 volts, respectively, limited by the current processing technique, a typically power management IC can normally accommodates a high voltage device of a single voltage rating, for example, 40 volts. As the voltage rating of a high voltage device becomes higher, the area occupied of the voltage rating also becomes larger. Hence, if a typical power management IC demands for the application of a device using different voltage ratings, different integrated circuits are required. The device's dimension must increase, which leads to a higher production cost.
Moreover, a LDMOS can be used as a switch device or an analog device. Normally, a switch device requires the generation of a sufficient current only in a split second of time to achieve the opening-and-closing function. However, an analog device requires a stable current for a longer period of time to avoid any a misinterpretation of a signal. Since the characteristic requirements for a switch device and an analog device are different, only a switch device or an analog device can be fabricated in a typical single LDMOS fabrication process, and a LDMOS that can concurrently accommodate the characteristic requirements of both a switch device and an analog device can not be achieved.
Accordingly, limited by the current process, a single IC chip that includes a LDMOS having only a single characteristic feature or a single voltage rating is restricted in its application. Further, the occupation of a large chip area by a single IC chip that includes a LDMOS results in high production cost.